MHD- Lec #3 - Ischemic Heart Disease

Question 1

State the myocardial infarction morphology during the following time frame:

1. 30 min - 4 hours
2. 4 - 12 hours
3. 12- 24 hours

Answer 1

1. No gross or light microscopic changes
2. Beginning coagulation necrosis
   - loss of nuclei (pyknosis)
3. Gross - Dark mottling (hyperemic myocardium)
   Ongoing coagulation necrosis
   Pyknosis of nuclei

Question 2

State the myocardial infarction morphology during the following time frame:

4. 1 - 3 days
5. 3 - 7 days
6. 7 - 10 days

Answer 2

1. Gross – mottled (red/yellow)
   Loss of nuclei and myocytes
   Neutrophil infiltrate
2. Myocyte disintegration, phagocytosis of dead cells (increased neutrophil infiltrate)
   YELLOW!

3.
Well-developed phagocytosis (macrophages) and early granulation tissue

Question 3

State the myocardial infarction morphology during the following time frame:

10 -14 days

2 - 8 weeks

Answer 3

Granulation tissue - neovascularization

2 - 8 weeks
Scar formation

Question 4

What are 3 laboratory tests for MI? Which is best?

Answer 4

1. Troponin I (most specific & sensitive)
2. CK
3. Myoglobin (low sensitivity)

Question 5

Describe stable & vulnerable plaques

Answer 5

Vulnerable plaques:
Lipid rich atheromas
Thin fibrous caps
Inflammation
Moderately stenotic - 50-75%

Stable plaque
- thick fibrous cap with mature dense collagen

Question 6

2 - Unstable Angina Pectoris

Answer 6

Atherosclerotic plaque disruption
Thrombogenic plaque components, subendothelial basement membrane exposed
Platelets activation, aggregation
Vasospasm
Partially occluding thrombus

Question 7

Stable (Typical) Angina Pectoris

Answer 7

Chronic stenosing coronary atherosclerosis (>75% reduction of lumen area)

Increased cardiac demand and workload needs unmet
Substernal chest pressure (ischemic myocytes = chest pain)
Physical activity, emotional excitement
Relieved with rest (decreased myocardial demand)
Vasodilator, nitroglycerin

Question 8

What are the signs and symptoms of left heart failure?

Right?

Answer 8

Left:

Paroxysmal Nocturnal dyspnea
Orthopnea
Pulmonary Edema

Right:
Heptomegaly
JVD
Peripheral Edema
Ascites

Question 9

Describe diastolic & systolic HF

Answer 9

Systolic
Deterioration of myocardial contraction
decreased EF* (60-70% is normal)
below 40% for systolic 
myocytes are unable to generate enough contractile force

Diastolic
Inability of heart chamber to relax, expand, and adequately fill during diastole

Question 10

3- Prinzmetal Variant Angina

Answer 10

Coronary artery spasm
Unrelated to physical activity, heart rate, blood pressure
Responds to vasodilators

TRANSMURAL and thus results in ST elevation (like an MI)

• but markers will not be present

Question 11

Occlusive thrombus formation results in what?

Answer 11

MI

Question 12

What is LDH and how does it change in an infarcted myocardium?

Answer 12

Triphenyltetrozolium chloride stain (LDH substrate)

Infarcted myocardium does not stain due to enzyme depletion (leakage

Question 13

What are the consequences of reperfusion injury? (3)

Answer 13

Reperfusion INJURY = Restoration of blood flow leads to local myocardial damage
Free radical production

1. Myocyte hypercontracture, increased Ca
2. Leukocyte aggregation proteases, elastases
3. Mitochondrial dysfunction  apoptosis

Question 14

Subendocardial transmural infarcts are often a result of what?

How does the infarct usually appear when the cause is global hypotension? (circumferential or transient/partial)

Answer 14

diffuse stenosing coronary artherosclerosis & reduction in coronary flow

• rarely evidence of plaque disruption or superimposed thrombus (thrombus may have been lysed prior to myocardial necrosis)

may result from prolonged and severe decrease in BP = SHOCK

2. hypotension results in CIRCUMFERENTIAL infarct